My MVC application contains a parent model, which will contain 1 or more child models.
I have set up the main view to display properties from the parent model, and then loop through a collection of my child models (of various types, but all inheriting from the same base type). Each of the child models have a corresponding partial view.
My "parent" view iterates over the child models like this:
foreach (ChildBase child in ViewData.Model.Children)
{
Html.RenderPartial("Partials/"+child.ChildType.ToString()+"Child",
section);
}
My application has the appropriate /Partials/ChildType1.ascx, ChildType2.ascx, etc. Everything works great.
Is this an appropriate way to use Partial Views? It feels slightly off-kilter due to the dynamic names, but I don't know another way to perform dynamic selection of the proper view without resorting to a big switch statement.
Is it advisable to use the same view for multiple "modes" of the same model? I would like to use the same .ascx for displaying the "read only" view of the model, as well as an edit form, based on which Controller Action is used to return the view.
Iconic,
It's difficult to answer the questions without knowing exactly what you're trying to achieve.
I'll have a go though:
If you're familiar with web forms, think of your partial view as a webforms usercontrol for the moment and think of the part of your model that is relevant to your partial views as a 'fragment of information' that want to pass across to the partial view.
Natural choices for using a partial view would be for elements used in many views across your site.
So ... in answer:
1.Although what you are doing is valid, it doesn't seem quite correct. An example of a partial view I have used might be a row in a grid of data where you'd call the partial view passing in the row object as its model:
foreach (MyObject o in Model.objects)
{
Html.RenderPartial("Shared/gridRowForObject.ascx", o, ViewData);
}
You can strongly type your views also to expect a specific type to be passed through as the Model object.
Again another use might be a login box or a 'contact me form' etc.
2._Ultimately this is a personal design decision but I'd go for the option that requires the least application/presentation logic and the cleanest code in your view. I'd tend to avoid writing to many conditional calls in your view for example and by inferring a base type to pass across to all of your partial views as in your example, may well tie you down.
When learning the MVC framework I found the Oxite code to be useful.
I hope that helps.
Related
I'm building my first MVC project and I have a question about the model.
Each webpage can only contain 1 model, yet my page will require 2 models, one is the search option (the ability to narrow your search such as selecting price range, colour etc) as well as the data.
Is it really as simple as creating a new Model, similar to a ViewModel which in this case would only have 2 properties, a SearchModel and a ProductModel?
Yes, there are really two "models" which is sometimes confusing. There's the "View Model" and the "Domain Model." The view model is passed directly to and from the view. The domain model describes the real-life domain that you're dealing with and is what the database persists. Often, they are the same thing, such as if you're displaying information for a single real domain object (e.g., a car). If you have two domain models that go on one page, you should make a view model with both as properties.
If you are looking to have two models in a view then this question might provide useful information:
multiple-models-in-a-view
Edit:
A good example is the 'Manage' view in the default 'Account' controller of a fresh mvc app. It uses a partial view to handle the changing of a user's password. Whilst both views are using the same model type it shows how to implement a partial view. In this case both the main view and the partial are submitting to the same method on the controller, hence they need to use the same model (which is a parameter for the controller method). But if the partial were to invoke a different controller method then the submitted model could be different. Hope this makes sense :)
I'm starting to develop a new ASP.NET MVC application, and I'd like to make sure that my understanding about the way of developing applications under MVC pattern is correct.
Question 1: Suppose that I have some main views (MainView1, MainView2, ...) with some partial views in it (PartialView1, PartialView2, PartialView3, ...). From what I have understood about MVC, I should define a Model for each view. e.g. I have to define PartialModel, PartialModel2, ... and also define my main models which are containers of the partial models which have been used in them:
public class MainModel1
{
public PartialModel1 Partial1 {get;set}
public PartialModel2 Partial2 {get;set}
public PartialModel3 Partial3 {get;set}
}
This way when I want to redirect to MainView, I can initialize the models used in that view by using this Model. Is my understanding of MVC correct? Or should communication between Views and Models be in another form in MVC?
Question 2: If the above is correct, Then suppose I have a partial view in some of my main view pages. This partial view has a submit button which calls an action method. This action method should somehow return the main page's view with the right viewmodels for views. Is there any recommendation about how to get/set viewmodels of other views in a partial view's action?
Thanks.
You understanding is correct. Each view (no matter whether it is main or partial) should have a corresponding view model (unless in the very rare case where this view contains only static html of course). And following this logic a main view that has to render other partial views will have a view model which itself will have reference (maybe as properties) to view models that are required by those partial views.
There is another technique which is using the Html.Action helper. In this case the partial is rendered through another controller/action than the main one. So you don't need to reference the partial view model in the main view model. They will be completely distinct. Take a look at the following blog post to learn more about Html.Action.
Your understanding is perfectly fine. This is what you can also refer to ViewModel in Asp.net MVC.
So, What basically is an Asp.net MVC ViewModel ?
In ASP.NET MVC, ViewModels allow you to shape multiple entities from one or more data models or sources into a single object, optimized for consumption and rendering by the view. The below image illustrates the concept of a ViewModel:
The purpose of a ViewModel is for the view to have a single object to render, alleviating the need for UI logic code in the view that would otherwise be necessary. This means the only responsibility, or concern, of the view is to render that single ViewModel object, aiding in a cleaner separation of concerns (SoC). Concerns are distinct aspects of the application that have a particular purpose (i.e., concern), and keeping these aspects apart means your application is more organized, and the code more focused. Putting data manipulation code in its own location away from the view and controller, enforces SoC.
Using ViewModels in MVC for finer granularity and better SoC leads to more easily maintainable and testable code. Remember, unit testing is about testing small units.
Along with better coding practices, there are many business reasons demonstrating why you might consider using ViewModels:
Incorporating dropdown lists of lookup data into a related entity
Master-detail records view
Pagination: combining actual data and paging information
Components like a shopping cart or user profile widget
Dashboards, with multiple sources of disparate data
Reports, often with aggregate data
This is a quite interesting question, in my opinion.
I have a strongly typed view using the WebForm view Engine, I don't know if changing to razor would solve my problem.
PROBLEM:
I have one view with a list of cars, so of type IList <Car>.
And I have a button "Create a new Car" that popups, the popup is a form that is hidded and you call a jQuery UI command $('formName').dialog() to popup it, this form has the attributes of the possible new car, so probably a new view with a strongly typed Car. After fill in the form the database should be populated with the new car, and the list of cars should be refreshed using Ajax.
The main problem is that I can't use HTML Helpers to IList <Car> and for Car at the same time.
Briefly: What is the strongly type for that view ? Is it possible to define two views and the other one call using pop-up? Changing it to Razor would solve my problem?
Best regards,
Tito Morais
Don't mix the views for listing the cars and creating a new car together.
For instance, you can make a popup that dynamically loads a "_CreateCar" partial view, using jQuery dialog or similar component. Then when the partial view is completed, reload the list view using another Ajax call.
Maybe not so much an elegant solution is to create a complex view model like:
class ListAndCreate
{
public IList<Car> AllCars {get;set;}
public Car NewCar {get;set;}
}
IMO this is correct since that one view is responsible for listing all cars and creating a new one. Now, I'm assuming that your NewCar has values coming from your controller or something, where you need to pass a model to your view.
The other approach, that #Jonas mentions is also correct and more unitized. You could create a partial view _CreateCar with type Car, render it with Jquery/Ajax to load it into a dialog/popup and have the form POST to a Create(Car c) method in your controller.
In Eric Hexter's Input Builders, different templates use different strongly-typed models; for example String uses PropertyViewModel<object>, DateTime uses PropertyViewModel<DateTime>, Form uses PropertyViewModel[], and so forth. Spark View Engine doesn't seem to allow this, because all elements that compose the presentation (masters, views, partials, etc.) are compiled into a single class.
If I try to setup a view involving more than one template, I get the following exception:
Only one viewdata model can be declared. PropertyViewModel<DateTime> != PropertyViewModel<object>
If leave just one viewdata declaration, I get another exception about the passed model item mismatching the required one.
It seems like I will have to give up either the Input Builders or Spark, which is sad because I really love both. So I thought I'd ask here to see if anybody has already figured this out.
Thanks.
You can always use <% Html.RenderPartial() %> for partial view rendering with different model. This will create more than one view class.
And what do you put in your View?
A recent blog from Scott Hanselman about using a special model binder for easier testing led me to think about the following:
What do you put in your controller logic building the view model, and what should be put in the view? what he does is this:
var viewModel = new DinnerFormViewModel {
Dinner = dinner,
Countries = new SelectList(PhoneValidator.Countries, dinner.Country)
};
return View(viewModel);
Now, I use the same way of passing data to my view, but I am unsure about how he deals with the Countries property. You could argue both sides:
Wrapping the Countries list in the SelectList prepares the data for the view, much like you create a viewmodel DTO to pass your data.
On the other hand, it somehow feels like you're specifically manipulating the data to be used in a dropdown list, limiting the way the view deals with your data from the controller.
I feel this is a bit of a gray area on the separation of concerns between the view and the controller, and I can't really decide which way to go. Are there any best practices for this?
PS: To keep it simple, let's assume the default ASP.NET MVC context, so basically your out of the box project. Default view engine and all that jazz.
In MVC (at least this flavor of it), one of the controller's responsibilities is to prepare the data for the view. So I think it is perfectly acceptable to prepare a specific model for the views consumption that implies it will be used in a drop-down. In this case the controller is just making it easier for the view and in fact prevents awkward code from having to otherwise be trickling into the view. It also keeps one from having those magic strings in the ViewData like VieData["Countries"].
So to sum up, while it may seem that there is some gray area in terms of responsibilities, ultimately that is the job of the controller: to interact with the view and to transform the domain model into other models that are easier to consume by the view.
Some suggest that having one all-encompassing view model per view is ideal (dubbed Thunderdome Principle).